Television set-top boxes are used to provide tuning capabilities for cable and satellite television systems. While these devices still provide that fundamental function, digital set-top boxes now often incorporate powerful computers in the latest generation of set-top boxes. With such computers available, it is now possible to expand the usefulness of the television set-top box beyond that of merely providing tuning functions for cable and satellite systems. Many set-top boxes now provide users with the ability to navigate the Internet using their television sets rather than a computer.
An on-screen user interface (UI) is commonly used with televisions and television set-top boxes for cable and satellite television systems to support numerous features. Features such as menus of favorite channels, locks and limits, timed recording, etc. as well as electronic program guides, pay-per-view (PPV) or video-on-demand (VOD) and other menus and guides are typically provided through such a user interface. In most instances, the user interface screens provided by televisions and television set-top boxes are bit map graphics with all of the behavior (navigation, state transition, etc.) implemented as software programs. Such programs are often coded in the “C” programming language or a variation thereof.
As the functionality of the user interface increases, the user interface structure becomes more complicated and the amount of coding required to support the on-screen user interface increases. Moreover, the amount of memory required by the graphics images grows and may become a cost issue due to the need to provide more memory within the device. In addition, even minor changes to the user interface specification generally require a code change making the design of such user interfaces extremely difficult to modify and inflexible.
In order to ameliorate these problems, some set-top boxes are being designed with Internet access capability. HTML (Hypertext Markup Language) user interface pages and a web browser are used to provide the user interface. This approach provides the advantages of reduced memory size to store user interface screens since HTML files are small compared with bit map graphics, flexibility to adopt changes since changing the user interface page design only requires changing the HTML files, and ease of creating a menu structure by using dynamic links. However, these advantages can be overshadowed by the disadvantages that the browser itself has a large memory footprint. Also, since the browser is optimized for Internet access, accessing local functions are not generally accommodated.
HTML by its very nature is designed to protect the resources of client computer from the outside. It is generally not possible to create an HTML file so that the loading of the file will directly access software outside the browser. In the case of an electronic programming guide, for example, it is easy to display a program guide page written in HTML but difficult to tune a channel by selecting a button on the program guide that requires access to local functions inside the set-top box.
In order to accommodate such functions requiring access to local resources within the set-top box, the interface between the browser and the remaining set-top box can be customized within the browser. This can be accomplished, for example, by defining special URLs that are trapped by the browser to call functions to lower level software (such as middleware or device drivers) before they are processed as normal URLs by sending an HTTP request to a server, for example. The special URL can be described as follows:    internal:function?<parameter1>value</parameter1><parameter2>value2</parameter2>
In this example the key word “internal” is trapped by the browser and the remainder of the string is translated to an internal function with two parameters. However, this solution also has drawbacks. Due to the requirement of modifying the browser source code, which is often produced by another party, in-depth knowledge of the code and access to the code is required. In addition, the special URL code required to implement this modification is outside the HTML standard. Finally, one URL is needed for each function to be accessed. For each URL addition the entire browser software generally requires recompiling.
An HTTP Microserver is sometimes provided as a part of a real time operating system. Such HTTP Microservers function in a manner similar to any other HTTP Server and are conventionally used to provide for remote system setup and diagnostics to permit access to internal API calls from outside computers via a TCP/IP network. Sometimes HTTP Microservers are also used to provide a display mechanism for a device that normally has no display of its own. Thus, a personal computer with a browser can be used to access a microserver on the device to monitor status or change settings. This function is used on devices such as printers and routers. In summary, HTTP Microservers conventionally provide the ability to access functionality from the outside of a device.